U.S. patent application number 11/732285 was filed with the patent office on 2007-11-15 for method and apparatus for sorting fine nonferrous metals and insulated wire pieces.
Invention is credited to Thomas A. Valerio.
Application Number | 20070262000 11/732285 |
Document ID | / |
Family ID | 38610044 |
Filed Date | 2007-11-15 |
United States Patent
Application |
20070262000 |
Kind Code |
A1 |
Valerio; Thomas A. |
November 15, 2007 |
Method and apparatus for sorting fine nonferrous metals and
insulated wire pieces
Abstract
A system for sorting fine nonferrous metals and insulated copper
wire from a batch of mixed fine nonferrous metals and insulated
wire includes an array of inductive proximity detectors, a
processing computer and a sorting mechanism. The inductive
proximity detectors identify the location of the fine nonferrous
metals and insulated copper wire. The processing computer instructs
the sorting mechanism to place the fine nonferrous metals and
insulated copper wire into a separate container than the
non-metallic pieces.
Inventors: |
Valerio; Thomas A.;
(Atlanta, GA) |
Correspondence
Address: |
DERGOSITS & NOAH LLP
FOUR EMBARCADERO CENTER, SUITE 1450
SAN FRANCISCO
CA
94111
US
|
Family ID: |
38610044 |
Appl. No.: |
11/732285 |
Filed: |
April 2, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60787797 |
Mar 31, 2006 |
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Current U.S.
Class: |
209/556 ;
209/559 |
Current CPC
Class: |
B07C 5/344 20130101 |
Class at
Publication: |
209/556 ;
209/559 |
International
Class: |
B07C 5/34 20060101
B07C005/34 |
Claims
1. A sorting apparatus for separating metal pieces from mixed
materials comprising: a conveyor belt for transporting mixed
material pieces; an array of inductive proximity sensors positioned
across the width of the conveyor belt and adjacent an upper surface
of the conveyor belt that emit magnetic fields and produce
electrical signals when the metal pieces are detected within
magnetic fields; a separation unit; and a controller coupled to the
plurality of inductive proximity sensors and the separation unit;
wherein when the controller receives the electrical signals for a
detected metal pieces, the controller instructs the separation unit
to separates the metal pieces that have been detected by the
plurality of inductive proximity sensors from the mixed material
pieces.
2. The sorting apparatus of claim 1 wherein the inductive proximity
sensors are high frequency inductive proximity sensors.
3. The sorting apparatus of claim 1 wherein the inductive proximity
sensors are separated into multiple rows of sensors by a distance
that prevents cross talk between the sensors and the sensors in
each of the adjacent rows are offset in a staggered manner.
4. The sorting apparatus of claim 1 wherein the array of inductive
proximity sensors includes a first group of inductive sensors that
operates at a first frequency and a second group of inductive
sensors that operates at a second frequency that is different than
the first frequency and the sensors of the first group are
positioned adjacent to the sensors of the second group.
5. The sorting apparatus of claim 1 wherein the separation unit
includes an air jet array that is mounted across an end of the
conveyor belt and deflects the metal pieces that fall off the end
of the conveyor belt.
6. The sorting apparatus of claim 5 further comprising: a first bin
for the metal pieces; and a second bin for the mixed pieces that
are not the metal pieces; wherein the air jet array deflects the
metal pieces into the first bin.
7. The sorting apparatus of claim 1 wherein the separation unit
includes an air jet array that is mounted across an end of the
conveyor belt and deflects the mixed pieces that are not the metal
pieces that fall off the end of the conveyor belt.
8. The sorting apparatus of claim 7 further comprising: a first bin
for the metal pieces; and a second bin for the mixed pieces that
are not the metal pieces; wherein the air jet array deflects the
mixed pieces that are not the metal pieces into the second bin.
9. The sorting apparatus of claim 1 wherein the controller includes
a signal strength algorithm that has filters signals from the
plurality of inductive proximity sensors by ignoring signals that
are less than a predetermined value and wherein the controller only
instructs the separation unit to separate the metal pieces only if
the signals associated with the metal pieces are greater than the
predetermined value.
10. The sorting apparatus of claim 1 wherein the array of inductive
proximity sensors are mounted in counter bored holes under an upper
surface of the conveyor belt and the positions of the sensors can
be adjusted so that the distance between each of the sensors and
the upper surface of the conveyor belt can be varied.
11. A sorting apparatus for separating metals from mixed materials
comprising: a surface for transporting the metals and the mixed
materials; an array of inductive proximity sensors that are mounted
in counter bored hole under the surface, wherein the sensors
produce electrical signals when metal pieces are detected within a
close proximity of the inductive proximity sensors; a separation
unit; and a controller coupled to the array of inductive proximity
sensors and the separation unit; wherein the controller instructs
the separation unit to separate the metals that have been detected
by the inductive proximity sensors from the mixed materials.
12. The sorting apparatus of claim 11 wherein each sensor is
mounted in a sensor hole and the array of inductive proximity
sensors includes a plurality of rows of sensors and the sensors in
the adjacent rows are offset so that the sensor detection areas of
the adjacent rows overlap by at least 20%.
13. The sorting apparatus of claim 11 wherein the array of
inductive proximity sensors includes a first group of inductive
sensors that operates at a first frequency and a second group of
inductive sensors that operates at a second frequency that is
different than the first frequency and the sensors of the first
group are adjacent to the sensors of the second group and the
sensors from the first group are positioned adjacent to the sensors
of the second group.
14. The sorting apparatus of claim 11 wherein the controller
includes a signal strength algorithm that has filters signals from
the array of inductive proximity sensors by ignoring signals that
are less than a predetermined value and wherein the controller only
instructs the separation unit to separate the metal pieces only if
the signals associated with the metal pieces are greater than the
predetermined value.
15. The sorting apparatus of claim 11 wherein the positions of the
inductive proximity sensors can be adjusted so that the distance
between each of the sensors and the upper surface of the conveyor
belt can be varied.
16. A sorting apparatus for sorting metal pieces from mixed
materials comprising: a surface for transporting the metals and the
mixed materials; a first array of inductive proximity sensors and a
second array of inductive proximity sensors that produce electrical
signals when the metals are detected within a detection range of
the inductive proximity sensors; a separation unit for separating
the metals from the mixed materials; and a computer coupled to the
plurality of inductive proximity sensors and the separation unit;
wherein a first array of inductive proximity sensors are mounted a
first distance under the surface and a second array of inductive
proximity sensors are mounted a second distance under the surface
and the computer instructs the separation unit to separate the
materials that have been detected by the first array of proximity
sensors or the second array of proximity sensors from the mixed
materials.
17. The sorting apparatus of claim 16 wherein if a first metal
piece is detected by the first array of inductive proximity sensors
but not detected by the second group of inductive proximity
sensors, the computer identifies the one piece is identified as
being a first type of metal and if a second metal piece is detected
by the first array of inductive proximity sensors and also detected
by the second array of inductive proximity sensors, the computer
identifies the second piece is identified as being a second type of
metal.
18. The sorting apparatus of claim 17 wherein the computer
instructs the sorting unit to place the first piece in a first
sorting bin and place the second piece in a second sorting bin.
19. The sorting apparatus of claim 16 wherein the first array of
inductive proximity sensors are mounted in counter bored holes
under an upper surface of the surface and the positions of the
sensors can be adjusted so that the distance between each of the
sensors and the surface can be varied.
20. The sorting apparatus of claim 16 wherein the sorting unit
includes an air jet array that is oriented across the width of the
conveyor belt and positioned adjacent to one end of the conveyor
belt.
21. The sorting apparatus of claim 16 further comprising: a sensor
plate made or wear resistant polymer with high abrasion factor and
low coefficient factor having a plurality of counter bored holes;
wherein the first array of inductive proximity sensors are mounted
in the plurality of counter bored holes.
22. The sorting apparatus of claim 16 wherein the surface for
transporting the metals and the mixed materials is the upper
surface of a conveyor belt that does not contain any carbon
materials and has a known thickness.
23. The sorting apparatus of claim 16 wherein each of the inductive
proximity sensors are mounted in holes and separated into staggered
multiple rows that are offset so that the detection area of a
sensor in a first row overlaps the detection area of a sensor in a
second row by less than 80%.
24. The sorting apparatus of claim 16 wherein the sensors are
mounted in holes and the first array of inductive proximity sensors
includes a plurality of rows and the sensor detection areas of a
first row are offset from the sensor detection areas of an adjacent
row by more than 20%.
25. The sorting apparatus of claim 16 wherein the array of
inductive proximity sensors includes a first group of inductive
sensors that operates at a first frequency and a second group of
inductive sensors that operates at a second frequency that is
different than the first frequency and the sensors of the first
group are adjacent to the sensors of the second group.
Description
BACKGROUND
[0001] Recyclable metal accounts for a significant share of the
solid waste generated. It is highly desirable to avoid disposing of
metals in a landfill by recycling metal objects. In order to
recycle metals from a mixed volume of waste, the metal pieces must
be identified and then separated from the non-metallic pieces.
Historically, fine pieces of stainless steel, aluminum/copper
radiators, circuit boards, low conductive precious and
semi-precious metals, lead, insulated wire and other nonconductive
scrap smaller than 40 mm in size have not been recoverable. What is
needed is a system that can separate fine pieces of stainless
steel, aluminum/copper radiators, silver circuit boards, lead,
insulated wire and other nonconductive scrap from other fine
non-metallic materials.
SUMMARY OF THE INVENTION
[0002] The present invention is a system and device for sorting
metal materials are smaller than 40 mm in size from a group of
mixed material pieces of similar size. The metals separated by the
system can include: stainless steel, aluminum/copper radiators,
circuit boards, low conductive precious and semi-precious metals,
lead, insulated wire and other nonconductive metals. The inventive
system utilizes arrays of inductive proximity sensors to detect the
target materials on a moving conveyor belt. The sensor arrays are
coupled to a computer that tracks the movement of the target
materials and instructs a separation unit to separate the target
materials as the reach the end of the conveyor belt.
[0003] In an embodiment, the fine pieces of stainless steel,
aluminum/copper radiators, circuit boards, low conductive precious
and semi-precious metals, lead, insulated wire and other
nonconductive scrap materials are placed on a thin conveyor belt
that transports the pieces over an array of inductive proximity
sensors. The inductive proximity sensors are arranged in one or
more arrays across the width of the conveyor belt and the path of
the materials. The sensors in the arrays are closely spaced but
separated enough to avoid "cross talk" which causes detection
interference between the adjacent sensors. The sensors may be
separated across the width and also staggered along the length.
This allows at least one of the sensors to detect target pieces
that are positioned anywhere across the width of the conveyor belt.
In addition to relative position, it is also possible to avoid
cross talk by using sensors that operate at different frequencies
and placing the different sensors adjacent to each other, possibly
in an alternating pattern. With more sensors placed across the
width, the system can more accurately determine the locations of
the target pieces.
[0004] Each sensor array can be configured to detect a specific
type of metal material. Different metal materials have different
"correction factors." This allows some materials to be more easily
detected by the inductive proximity sensors than other materials.
Each array of sensors spans the width of the material travel path
and is intended to detect a specific type of material. Each array
can use sensors having multiple frequencies or separate staggered
rows to avoid cross talk. It is also possible to have the sensors
of multiple arrays mixed within a region of the material
transportation system.
[0005] The inductive proximity sensors are positioned so that they
face upward towards the upper surface of the conveyor belt. The
sensors have a penetration distance which is the maximum distance
that the sensor can detect a specific type of material. The
penetration distance can range from less than 22 millimeters (mm)
to greater than 40 mm. Different materials have different detection
distances which are represented by a "correction factor." The
correction factors may range from 0 to 1.0+. The detection range of
a sensor is multiplied by the correction factor to determine the
material detection range.
[0006] When the target pieces travel closely over the array of
sensors, at least one of the sensors will generate an electrical
signal. However, in some embodiments, it may be desirable to not
detect some target materials. This can be achieved by controlling
the depth of the sensors under conveyor belt. When the sensors are
placed close to the conveyor belt surface, all sensors will detect
all target materials. However, when the sensors are placed a
distance under the surface, the sensors may detect materials having
a high correction factor but not detect materials that have a lower
correction factor. The system can be configured with multiple
arrays of sensors that selectively detect, identify and distinguish
different types of materials. For example, a first array of sensors
may be placed close to the upper surface and a second array of
sensors may be recessed below the surface. The first array detects
all target materials and the second array only detects target
materials having high correction factors. The system can then use
this information to not only separate the target materials but also
separate the high correction factor materials from the low
correction factor materials.
[0007] A computer or other processor is coupled to the sensor
arrays. The processor determines which sensor in the array detects
the target piece and then correlates the position of the target
materials across the width of the conveyor belt. The system also
knows the speed of the conveyor belt and the distance between the
sensors and the end of the conveyor belt. The time that a target
piece reaches the end of the conveyor belt is determined by the
distance divided by speed and the position of the target piece
across the width is determined by the specific sensor detection in
the array. The system will then predict when and where the piece
will come to the end of the conveyor belt.
[0008] The computer uses the target material location information
to control a sorting system. The computer instructs the sorting
unit to selectively remove the piece at the detected width position
at the predicted time. In an embodiment, the sorting system
includes an array of air jets mounted at the end of the conveyor
belt. When the fine stainless steel, aluminum/copper radiators,
circuit boards, low conductive precious and semi-precious metals,
lead, insulated wire and other nonconductive scrap pieces are
detected, the computer synchronizes the actuation of the air jet
with the time that the metal piece reaches the end of the conveyor
belt. More specifically, one or more air jets corresponding to the
position of the target piece are actuated to deflect the target
piece as it falls off the conveyor belt. The target pieces are
deflected into a separate recovery bin. The air jets are not
actuated when non-metallic pieces reach the end of the conveyor
belt and fall into a bin containing non-metallic pieces. The sorted
fine nonconductive nonferrous metal piece and insulated wire pieces
can then be recycled or resorted to separate the different types
metals.
[0009] As discussed above, it is possible to selectively detect
different types of target materials based upon their correction
factors. In this type of a system, the force of the air jets may be
controlled. While the non-metallic materials may fall into a scrap
bin without any air jet actuation, the system may apply different
air jet forces depending upon the type of material detected. For
example, a low correction factor piece may get a low force air jet
and be deflected into a first sorting bin while a high correction
factor piece may be get a more powerful air jet and be deflected
into a second sorting bin.
[0010] In alternative embodiments, multiple conveyor belt sorting
systems can be used to perform multiple sortings based upon the
different correction factor materials. The first sorting system may
separate target metals from non-metals. The target metals may then
be placed on a second conveyor belt and passed over a second array
of sensors that selectively detect high correction factor
materials. The system would then separate the high correction
factor materials from the lower correction factor materials.
Additional sorting can be performed as desired. This is more
accurate sorting is helpful in segregating: steel, aluminum, copper
and brass which makes recycling more efficient.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a single sort embodiment of the present
invention;
[0012] FIG. 2 is a single sort embodiment of the present
invention;
[0013] FIG. 3 is a multiple sort embodiment of the present
invention;
[0014] FIG. 4 is a multiple belt and multiple sort embodiment of
the present invention;
[0015] FIG. 5 is a top view of a staggered sensor array;
[0016] FIG. 6 is a top view of a mixed frequency sensor array;
and
[0017] FIG. 7 is a top view of a four row staggered sensor
array.
DETAILED DESCRIPTION
[0018] Although the present invention is primarily directed towards
a sorting system that utilizes inductive proximity sensors to
identify and separate target metal pieces, there are other system
components that are useful in optimizing the system performance.
The mixed materials used by the inventive system are ideally small
or fine pieces. These can come from various sources. In an
embodiment, the mixed materials are emitted from a shredder and
sorted by size with a trommel or another type of screening device
that separates small pieces from larger pieces. In the preferred
embodiment, pieces that are smaller than 40 mm (millimeters) are
separated from pieces that are larger than 40 mm.
[0019] These fine pieces are further processed to separate the
ferrous and conductive nonferrous materials. The mixed fine pieces
can be passed over a magnetic separator that removes the magnetic
ferrous materials. The fine nonferrous materials are then passed
over an eddy current separator to remove the conductive nonferrous
materials. Other metal sensors can be used to remove the other
non-conducting metals that may have been missed by the eddy current
device.
[0020] Various other processes can be performed to separate or
prepare the remaining mixed materials for processing by the
inventive system. For example, a density sorting device can be used
to separate the lower density materials such as plastics, rubber
and wood products from higher density glass and metals. An example
of a density sorting system is a media flotation system, the pieces
to be sorted are immersed in a fluid having a specific density such
as water. The plastic and rubber may have a lower density and float
to the top of the fluid, while the heavier metal and glass
components with a higher density will sink.
[0021] After the ferrous and conductive nonferrous materials have
been removed, the remaining fine nonconductive and nonferrous metal
materials are passed by an array of sensors that can separate the
nonferrous metals and insulated copper wire from the remaining
materials. The sensors are able to detect the nonferrous metals
including: stainless steel, aluminum/copper radiators, circuit
boards, low conductive precious and semi-precious metals, lead and
other nonconductive materials. In the preferred embodiment, these
target pieces are between about 1 mm and 40 mm in size. The
inventive system is a significant improvement over the prior art
that has difficulty even detecting non-ferrous metal pieces that
are less than 40 mm in size.
[0022] Other recycling systems detect and separate the metal pieces
from the mixed material parts. As discussed in U.S. patent
application Ser. No. 11/255,850, which is hereby incorporated by
reference, the metal pieces are detected with inductive proximity
detectors. The proximity detector comprises an oscillating circuit
composed of a capacitance C in parallel with an inductance L that
forms the detecting coil. An oscillating circuit is coupled through
a resistance Rc to an oscillator generating an oscillating signal
S1, the amplitude and frequency of which remain constant when a
metal object is brought close to the detector. On the other hand,
the inductance L is variable when a metal object is brought close
to the detector, such that the oscillating circuit forced by the
oscillator outputs a variable oscillating signal S2. It may also
include an LC oscillating circuit insensitive to the approach of a
metal object, or more generally a circuit with similar
insensitivity and acting as a phase reference.
[0023] Oscillator is powered by a voltage V+ generated from a
voltage source external to the detector and it excites the
oscillating circuit with an oscillation with a frequency f
significantly less than the critical frequency fc of the
oscillating circuit. This critical frequency is defined as being
the frequency at which the inductance of the oscillating circuit
remains practically constant when a ferrous object is brought close
to the detector. Since the oscillation of the oscillating circuit
is forced by the oscillation of oscillator the result is that
bringing a metal object close changes the phase of S2 with respect
to S1. Since the frequency f is very much lower than the frequency
fc, the inductance L increases with the approach of a ferrous
object and reduces with the approach of a non-ferrous object.
Inductive proximity sensors are described in more detail in U.S.
Pat. No. 6,191,580 which is hereby incorporated by reference.
[0024] Different types of inductive proximity detectors are
available which have specific operating characteristics. For
example, high frequency unshielded inductive proximity sensors
(.about.500 Hz up to 2,000 Hz) can detect fine nonferrous metals
and insulated copper wire pieces. In an embodiment, the inductive
proximity sensors used to detect the fine stainless steel,
aluminum/copper radiators, circuit boards, low conductive precious
and semi-precious metals, lead, insulated wire and other
nonconductive scrap operates at a frequency of about 500 Hz and
penetrate to 22 mm for increased detection resolution. The
operating frequency corresponds to the detection time and operating
speed of the metal detection. The faster operating frequency of 500
Hz allows the sensor to detect metal objects more quickly than a
normal analog sensor. Because the high frequency sensors operate
very quickly, they may generate more noise which results in output
errors and possibly misfiring of the sorting system. Filters can be
used to remove the noise, but the filters add additional components
and degrade the fast operation of the high frequency sensors. In
contrast, the analog sensors may collect data at a fast rage 0.5
milliseconds, but the data output is inherently filtered which
averages of the detection signal and can provide a more reliable
output.
[0025] Another distinction between the sensors is the penetration
distance. The analog sensor may have a penetration distance of 40
mm while the high frequency sensor may have a penetration distance
of 22 mm. The penetration distance is the distance that the sensor
can detect target materials that have a 1.0 correction factor.
Other differences between analog inductive proximity detectors and
the custom high frequency inductive detectors are specified in
Table 1 below. TABLE-US-00001 TABLE 1 Analog Inductive High
Frequency Inductive Proximity Detector Proximity Detector Operating
Frequency .about.100 Hz .about.500 Hz Resolution .about.25 mm at
2.5 mps .about.12 mm at 2.5 mps Penetration 40 mm 22 mm Diameter
.about.30 mm .about.18 mm Detection Time .about.10 ms per cycle
.about.5 ms per cycle
[0026] In an embodiment, the high frequency inductive proximity
sensors are coil based and are able to accurately detect
non-ferrous metals such as aluminum, brass, zinc, magnesium,
titanium, and copper. Although inductive proximity detectors can
detect the presence of various types of metals, this ability can
vary depending upon the sensor and the type of metal being
detected.
[0027] The distinction in sensitivity to specific types of metals
can be described in various ways. One example of the variation in
sensitivity based upon the type of metal being detected is the
correction factor. The inductive proximity sensors can have
"correction factors" which quantifies the relative penetration
distance for various metals. By knowing the base penetration
distance is 22 mm and the correction factor of the metal being
detected, the penetration distance for any metal being detected can
be determined. Typical correction factors for fine nonferrous
metals are listed below in Table 2. TABLE-US-00002 TABLE 2 METAL
CORRECTION FACTOR Aluminum 0.50 Brass 0.45 Copper 0.40
Nickel-Chromium 0.90 Stainless Steel 0.85 Steel 1.00
[0028] As discussed above, the high frequency inductive proximity
sensor has a penetration rating of 22 mm and as shown in Table 2,
the aluminum correction factor is 0.50. Thus, the penetration
rating for aluminum would be the correction factor 0.50 multiplied
by the penetration rating 22 mm. Thus, the penetration depth for
aluminum for the detector is 11 mm.
[0029] In order to accurately detect the fine stainless steel,
aluminum/copper radiators, circuit boards, low conductive precious
and semi-precious metals, lead, insulated wire and other
nonconductive scrap pieces mixed in with fine non-metallics, the
detectors must be placed in close proximity to these target
materials. The mixed pieces are preferably distributed on a
conveyor belt in a spaced apart manner so that the fine pieces are
not stacked on top of each other and there is some space between
the pieces. The batch of mixed materials is then moved over the
array(s) of detectors that span the width of the conveyor belt.
Because the detection range of the metal detectors is short, the
inductive proximity sensors must be positioned close to each other
so that all metal pieces passing across the array of sensors are
detected. The fine pieces should not be able to pass between the
sensors so as to not be detected.
[0030] With reference to FIG. 1, a side view of an embodiment of
the inventive sorting system is shown. In order to quickly and
accurately detect all of the fine nonferrous metals and insulated
copper wire, the mixed fine materials pieces 103, 105 should be
passed in close proximity to at least one of the first frequency
sensors 207 or second frequency sensors 209. The conveyor belt 221
should be thin and not contain any carbon material so that sensors
207, 209 mounted in counter bore holes 237 in a sensor plate 235
under the conveyor belt 221. The conveyor belt 221 slides over the
smooth upper planar surface sensor plate 235. The counter bore
holes 237 allow the sensors 207, 209 to be mounted below the
conveyor belt 221 so there is no physical contact. In the preferred
embodiment, the conveyor belt 221 is made from a thin layer of
urethane or urethane/polyvinyl chloride, which provides a non-slip
surface for the mixed material pieces, and is about 0.9 mm to 2.5
mm thick depending on the desired penetration 103, 105. The belt
preferably travels at a speed of about 0.9 meters per second (mps)
to 4 mps depending on the desired resolution. A faster speed will
require more accurate detection than a slower moving conveyor belt.
The sensor plate 235 is preferably made of a wear resistant polymer
with a high abrasion factor and low coefficient factor, such as
polytetrafluoroethylene (Teflon) or a polycarbonate such as Lexan
and is about 0.5 mm to 1.2 mm thick depending on the desired
penetration.
[0031] Because the materials being sorted are small, the nonferrous
metals and insulated copper wire 105 tend to lie flat on the
conveyor belt 221 and will pass close to the inductive proximity
sensor arrays 207, 209 mounted under and across the width of the
conveyor belt 221. Because the fine stainless steel,
aluminum/copper radiators, circuit boards, low conductive precious
and semi-precious metals, lead, insulated wire and other
nonconductive scrap pieces 105 are small, a large percentage of the
available area will rest on the belt 221. In alternative
embodiments, additional inductive proximity sensor arrays are
placed above the conveyor belt 221 facing down onto the mixed fine
materials 103, 105. These upper sensors 207, 209 can be arranged in
the same manner as the sensors 207, 209 under the belt. All signals
from the detectors 207, 209 are fed to a processing computer
225.
[0032] The detected positions of the fine stainless steel,
aluminum/copper radiators, circuit boards, low conductive precious
and semi-precious metals, lead, insulated wire and other
nonconductive scrap 105 are fed to the computer 225. By knowing the
positions of the fine stainless steel, aluminum/copper radiators,
circuit boards, low conductive precious and semi-precious metals,
lead, insulated wire and other nonconductive scrap 105 on the belt
and the speed of the conveyor belt 221, the computer 211 can
predict the position of the fine stainless steel, aluminum/copper
radiators, circuit boards, low conductive precious and
semi-precious metals, lead, insulated wire and other nonconductive
scrap 105 at any time after detection. For example, the computer
225 can predict when and where a fine stainless steel,
aluminum/copper radiators, circuit boards, low conductive precious
and semi-precious metals, lead, insulated wire and other
nonconductive scrap 105 will fall off the end of the conveyor belt
221. With this information, the computer 225 can then instruct the
sorting mechanism to separate the fine stainless steel,
aluminum/copper radiators, circuit boards, low conductive precious
and semi-precious metals, lead, insulated wire and other
nonconductive scrap 105 as it falls off the conveyor belt 221.
[0033] Various sorting mechanisms may be used. Again with reference
to FIG. 1, an array of air jets 217 is mounted at the end of the
conveyor belt 221. The array ofairjets 217 is mounted under the end
of the conveyor belt 221 and has multiple air jets mounted across
the conveyor belt 221 width. The computer 225 tracks the position
of the fine stainless steel, aluminum/copper radiators, circuit
boards, low conductive precious and semi-precious metals, lead,
insulated wire and other nonconductive scrap pieces 105 and
transmits a control signal to actuate the individual air jet within
the array 217 corresponding to the position of the fine stainless
steel, aluminum/copper radiators, circuit boards, low conductive
precious and semi-precious metals, lead, insulated wire and other
nonconductive scrap 105 as they fall off the end of the conveyor
belt 221. The air jets 217 deflect the fine stainless steel,
aluminum/copper radiators, circuit boards, low conductive precious
and semi-precious metals, lead, insulated wire and other
nonconductive metal scrap 105 and cause them to fall into a metal
collection bin 229. The air jets 217 are not actuated when
non-metal pieces 103 come to the end of the conveyor belt 221 and
fall off the end of the conveyor belt 221 into a non-metal
collection bin 227.
[0034] It is also possible to have a similar sorting mechanism with
an array of jets mounted over the conveyor belt. With reference to
FIG. 2, an alternative sorting system includes an array of jets 551
mounted over the conveyor belt 221. The operation of this sorting
system is similar to the system described with reference to FIG. 4.
The difference between this alternative embodiment is that as the
metal pieces 105 fall off the end of the conveyor belt 221, the
computer 211 actuates the array of jets 551 to emit air jets 553
that are angled down to deflect the target metal pieces 105. This
results in the metal pieces 105 being diverted into a first bin 229
for stainless steel, aluminum/copper radiators, circuit boards, low
conductive precious and semi-precious metals, lead, insulated wire
and other nonconductive metal scrap and a second bin 227 for all
other materials.
[0035] Current air jets have operating characteristics that can
cause inefficiency in the sorting system. Specifically, because the
pieces come across the conveyor belt at high speed, the actuation
of the air jets must be precisely controlled. Although the computer
may actuate the air valve, there is a delay due to the valve's
response time. A typical air valve is connected to 150 psi air and
has a Cv of 1.5. While performance is constantly improving, the
current characteristics are 6.5 milliseconds to open the air valve
and 7.5 milliseconds to close the air valve. The computer can
compensate for this delayed response time by calculating when the
stainless steel, aluminum/copper radiators, circuit boards, low
conductive precious and semi-precious metals, lead, insulated wire
and other nonconductive scrap will reach the end of the conveyor
belt and transmitting control signals that account for the delayed
response time of the air valve. This adjustment can be done through
computer software. For example, the signal to open the air valve is
transmitted 6.5 milliseconds before the piece reaches the end of
the conveyor belt and the signal to close the valve 7.5
milliseconds before the air jet should be stopped. With this
technique, the sorting of the pieces will be more accurate. Future
air valves will have an opening response time of 3.5 milliseconds
and a closing response time of 4.5 milliseconds. As the response
time of the air valves further improves, this off set in signal
timing can be adjusted accordingly to preserve the timing
accuracy.
[0036] Although the inventive metal sorting system has been
described with an array of air jets mounted over or under the
conveyor belt, it is contemplated that various other sorting
mechanisms can be used. For example, an array of vacuum hoses may
be positioned across the conveyor belt and the computer may actuate
a specific vacuum tube as the metal pieces pass under the
corresponding hose. Alternatively, an array of small bins may be
placed under the end of the conveyor belt and when a stainless
steel, aluminum/copper radiators, circuit boards, low conductive
precious and semi-precious metals, lead, insulated wire and other
nonconductive scrap piece is detected, the smaller bin may be
placed in the falling path to catch the metal and then retracted.
In this embodiment, all non-metal pieces would be allowed to fall
into a lower bin. It is contemplated that any other sorting method
can be used to separate the metal and non-metal pieces. Various
other sorting mechanisms may be used.
[0037] Each sensor array is intended to detect a specific type of
material. Because different types of metal have different
correction factors, it is possible to distinguish the type of
materials using multiple sensor arrays. Each sensor has a
"detection area" which is the area that the sensor can detect a
target material. The detection area is circular and emanates from
the sensor in a conical volume. Thus, the detection area will
expand with distance from the material transportation surface,
however beyond a detection distance the sensor will not detect
target materials. In order to properly cover the entire width of
the material transportation surface, the detection areas of the
sensors in the adjacent rows should be overlapped.
[0038] In the following examples, multiple sensor arrays are used
to separate not only metal and non-metal pieces, but also different
types of target metal materials. This is accomplished by using
multiple sensor arrays having different settings. Each array is a
group of sensors that are set to the same material detection
properties. Although, the sensors within each array can be
identical, it is also possible to mix different sensors within an
array. For example, sensors can have different frequencies,
operating characteristics (analog/digital), staggered spacing, etc
and still be part of the same sensor array. It is also possible to
position the sensors from different arrays within an overlapped
region of the inventive system, so that one area of sensors can
have sensors associated with multiple sensor arrays.
[0039] With reference to FIG. 3, in an embodiment, the system has a
plurality of inductive sensor arrays 305, 307, 309 that run across
the width of the conveyor belt 221. The inductive sensors arrays
305, 307, 309 are also positioned at different depths 315, 317, 319
so that at least one array 305 will detect all targeted materials
while one or more other arrays 307, 309 will only detect some
materials that have a relatively high correction factor.
[0040] As discussed above in table 1, the penetration distance for
a high frequency digital sensor is about 22 mm and the correction
factors for the different materials listed in Table 2 range from
1.0 for steel to 0.40 copper. Thus, the correction factors cause
the sensors to be more sensitive to some materials. By placing the
sensors at a depth below the surface used to transport the mixed
materials, the sensors can selectively detect different types of
materials. For example, a sensor will be able to detect steel
within a 22 mm penetration depth placed 10 mm under the material
conveyor surface will only be able to detect steel, stainless steel
and nickel chromium. The sensors will not be able to detect copper
pieces because copper has a correction factor of 0.4. When
multiplied by the penetration depth of 22 mm the range is reduced
to 8.8 mm. Since the sensor is 10 mm below the copper pieces, it
cannot detect copper. A listing of penetration depths for different
materials and sensors is listed below in Table 3. TABLE-US-00003
TABLE 3 Analog Digital High Sensor Detection Frequency Sensor
Material Distance (40 mm) Detection Distance (22 mm) Aluminum 20 mm
11 mm Brass 18 mm 9.9 mm Copper 16 mm 8.8 mm Nickel-Chromium 36 mm
19.8 mm Stainless Steel 34 mm 18.7 mm Steel 40 mm 22 mm
[0041] The difference in sensitivity to different material can be
used by the inventive system to sort the different types of target
materials. In an embodiment, the analog and high frequency digital
sensors can be used for different sensor arrays 305, 307, 309. In
the inventive system, with reference to FIG. 3, the first array of
high frequency digital sensors 305 are placed near the top of the
conveyor belt 221, for example 5 mm below the surface 315. Because
all materials listed in Table 2 have a correction factor of at
least 0.40, the sensor penetration depth of the high frequency
sensor is at least 8.8 mm. Since the first sensor array 221 is
placed 5 mm 315 under the surface, it will be able to detect the
presence of all listed materials. A second array of analog sensors
307 is placed 19 mm 317 below the surface. The second array 307 has
a penetration depth of 40 mm and will be able to detect target
pieces that have an analog sensor detection distance of 19 mm or
greater.
[0042] Another way to determine the position of the sensors is by
correction factor. By placing the analog sensors 19 mm below the
conveyor belt surface, the sensors will only detect materials that
have a correction factor greater than 0.475. This correction value
transition point is calculated by 19 mm (distance)/40 mm
(penetration)=0.475 correction factor. The materials that are
detectable by the second array include: aluminum, nickel-chromium,
stainless steel and steel.
[0043] The third array 309 may use high frequency digital sensors
and may be placed 15 mm 319 under the conveyor belt surface. The
high frequency sensors will be able to detect nickel-chromium,
stainless steel and steel which all have sensor detection distances
greater than 15 mm and correction factors greater than 0.68. The
correction factor transition point is calculated by 15 mm
distance/22 mm penetration=0.68 correction factor.
[0044] The sensor arrays 305, 307, 309 are coupled to a computer
301 that determines the type of material and determines when the
target materials will reach the end of the conveyor belt. In this
configuration, the target pieces may be detected by some sensor
arrays 305, 307, 309 but not all arrays. The summary of the sensor
array 305, 307, 309 detection is summarized in Table 4.
TABLE-US-00004 TABLE 4 First Array Third Array High Frequency
Second Array High Frequency Material Digital Analog Digital
Aluminum Detected Detected Not Detected Brass Detected Not Detected
Not Detected Copper Detected Not Detected Not Detected
Nickel-Chromium Detected Detected Detected Stainless Steel Detected
Detected Detected Steel Detected Detected Detected Non-Target Not
Detected Not Detected Not Detected Materials
[0045] Because the computer 301 is coupled to each sensor array
305, 307, 309, it can narrow the type of material to a small group
or identify the material based upon the sensor arrays 305, 307, 309
that detect the material. The computer 301 can use the sensor array
305, 307, 309 information to instruct the sorting unit to separate
each group of identified materials into separate sorting bins 333,
335, 337, 339. In an embodiment, materials 323 that are not
detected by any of the sensor arrays 305, 307, 309 are not target
metal materials. Because these materials 323 are not detected they
will fall off the conveyor belt into a first bin 333. Material
pieces that are detected by only the first array 305 are limited to
brass or copper 325 and may be deflected by the air jet array 303
into a second bin 335. Pieces that are detected by both the first
and second arrays 305, 307 can only be aluminum 327 which is
deflected into a third bin 337. Pieces that are detected by all
three sensor arrays 305, 307, 309 are either nickel-chromium,
stainless steel or steel pieces 329 that are deflected into a
fourth bin 339.
[0046] Although it may be more efficient to have a single conveyor
belt system that sorts pieces into many different types of
materials, it may be more accurate to use multiple conveyor belts
to simply the sorting unit requirements. With reference to FIG. 4,
a system that utilizes two conveyor belts 421, 423 is illustrated.
In this embodiment, a high frequency array of sensors 407 is used
in the first conveyor belt 421 to separate all target metal pieces
325, 327, 329 from the non-target pieces 323. The non-target pieces
323 fall into a first bin 333 while the target metal pieces 325,
327, 329 are detected and deflected by the first sorting system 403
onto a second conveyor belt 423. The second conveyor belt 423 has a
second array 409 and a third array 411 of sensors. These may both
be analog sensor arrays that are set at depths of 17 mm and 38 mm,
respectively. The computer 401 can instruct the second sorting unit
405 to separate the parts 345, 347, 349 based upon these transition
points. The target pieces 325 such as copper that have a detection
distance of 16 mm or less will fall into the second bin 345. The
pieces 327 that have a detection distance between 17 and 38, brass,
copper, nickel-chromium and stainless steel can be deflected into
the third bin 347. The steel pieces that have a detection distance
greater than 38 are detected by both the second and third array of
sensors are deflected into the fourth bin.
[0047] While two examples have been described, various other
configurations are possible. The system may include any number of
conveyor belts may be used with any number of sensor arrays. For
example, since there are six types of materials, the inventive
system may include six conveyor belts that each have one array of
sensors. In this embodiment, the first sensor may separate
non-target materials, the second sensor may separate steel, the
third may separate stainless steel, etc. By only having a single
sensor per conveyor belt, the separation unit operation is
simplified since it only has a single jet force when actuated.
Although the system has been described as using each array to
distinguish each different type of target material, it is also
possible to have redundant sensor arrays that have the same or
similar switch points to improve system accuracy. In some cases,
different sensors are better at detecting different shapes or sizes
of target materials. For example, a high frequency sensor may
detect smaller target materials because it is able to take many
samples in a short period of time, however the high frequency may
also result in more noise errors. By running a lower frequency
analog array and a high frequency digital array at the same switch
point, the detection of the target materials in the sensor range
might be improved.
[0048] Although the sensors are disclosed as having a fixed
penetration distance, these values may vary or shift depending upon
the operating conditions, the type of sensor or manufacturing
variations. Because the penetration distance may not uniform, it
may be desirable to have an adjustable sensor position. As
discussed above, the sensors are placed at specific distances below
the upper surface of the conveyor belt typically in a counter bored
hole. In an embodiment, the sensor is threaded or mounted in a
threaded cylinder and the counter bored holes have corresponding
threads. Each sensor is adjustable by screwing the sensor in or out
of the threaded hole. Various other sensor adjustment methods and
mechanisms can be used including: micro adjusting linear actuators,
shims, adjustable friction devices, etc.
[0049] In an embodiment, the inventive system has a calibration
procedure in which the sensor positions are adjusted to provide a
uniform output for a given target material. A reference target
piece is placed over each sensor in the array in the same relative
position and the output of the sensor is checked for uniformity.
Alternatively, a test pattern of test materials may be passed over
the sensor arrays in a specific manner. The individual sensors are
adjusted so that the proper output is obtained from each.
[0050] In an embodiment, it maybe necessary to perform calibration
of the sensors. Because the outputs for analog and digital devices
are substantially different individual calibration procedures might
be required for each. For an analog device, the output can be a
voltage within a specific range such as 0 to 10 volts or current
ranging from 4 to 20 milli Amps. The analog sensors are adjusted so
that the outputs for a calibration object is within a narrow
acceptable range. Multiple calibration objects can be used. In
contrast, a digital sensor will be switched on or off in response
to a target object. The calibration method may require separate
"on" and "off" calibration objects that are similar. If the on" and
"off" calibration objects are very similar the digital sensors will
be more uniform in output. During testing, the sensors must be
adjusted so that they switch on when the on calibration object is
used and off when the off calibration object is used. Once all the
sensors are calibrated, the system should perform with a high level
of uniform selectivity. The described calibration process may need
to be repeated as the system and sensors may fluctuate over
time.
[0051] Although it is desirable to place the sensors close to each
other this close proximity may result in "cross talk" which is a
condition in which detection signals that are intended to be
detected by only one sensor may detected by other adjacent
detectors. The result can include sensor location and sorting
errors that result in sorting errors. The computer separate both
the target and the improperly targeted pieces as they reach the end
of the conveyor belt. There are various methods for avoiding the
cross talk between the detectors while monitoring the entire width
of the conveyor belt.
[0052] Cross talk can only occur between sensors operating at the
same frequency. In the preferred embodiment, cross talk is avoided
by spacing the sensors away from each other. With reference to FIG.
5, an array of sensors 503 is illustrated that spans the width of a
conveyor belt 501 includes first row of sensors 505 that are
uniformly spaced apart from each other and a second parallel row of
sensors 507 that are offset from the first row of sensors 505.
Thus, the detection areas of the 500 Hz sensors can be placed in an
overlapping position without cross talk. This allows the sensors in
each row to be very closely spaced across the width of the parts
path.
[0053] In other embodiments, it is possible to use sensors that
operate at two or more frequencies. Cross talk may occur between
sensors that have detection area overlap and are operating at the
same frequency. If sensors having different frequencies are mixed
within the array, it is possible to sufficiently separate the
sensors that operate at the same frequency to avoid cross talk.
With reference to FIG. 6, an array of sensors 513 spans the width
of the conveyor belt 511. Since the adjacent sensors 515, 517
operate at different frequencies they many be placed close
together. The first frequency sensors 515 are sufficiently
separated and similarly the second frequency sensors 517 are
sufficiently separated to prevent cross talk.
[0054] In other embodiments, the array can include sensors
operating at multiple frequencies and sensors that are staggered
across the belt so that sensors are located across the entire
width, but are separated from each other. For example, an array can
include a first set of sensors operates at a first frequency, a
second set of sensors operates at a second frequency, and a third
set of sensors operates at a third frequency. These different
sensors can be configured in an alternating pattern across the
width of the conveyor belt. By using different frequencies and/or
using multiple staggered rows of sensors, fine stainless steel,
aluminum/copper radiators, circuit boards, low conductive precious
and semi-precious metals, lead, insulated wire and other
nonconductive scrap can be detected at any point across the width
of the conveyor belt. Although the system has been described with
separate arrays of sensors, it is possible to mix the sensors set
at different depths and different types and frequencies all within
one or more strips that span the width of the conveyor belt.
Although the wiring of this type of a mixed system will be
complicated, it will have the benefit of placing dissimilar sensors
in close proximity so that cross talk is minimized.
[0055] With reference to FIG. 7, in an embodiment, an individual
array 703 includes 128 sensors 707 that are located in four offset
rows 705. The materials being detected would travel in a vertical
direction across the array 703. Each row of sensors 705 runs across
the width of the conveyor belt 701. In this embodiment, the sensors
707 may be mounted within counter bored holes that are 38 mm in
diameter and 19 mm deep. The sensor holes are separated by a center
to center distance of 72 mm within each row 705. Each row 705 is
separated by a distance of 109 mm and the sensors 707 in the
adjacent rows are offset by 18 mm. This configuration places
sensors 707 across the entire width with some overlap between the
sensors 707 and also provides sufficient separation to avoid cross
talk between the sensors 707. During experimentation, identical
high frequency 500 Hz sensors were used without any cross talk
between sensors.
[0056] The sensors are able to detect all target materials that are
placed over the 38 mm diameter counter bored hole that are within
the detection range. In the described embodiment, there is some
overlap between the counter bore hole diameters of the sensors rows
across the width of the array that spans the parts path. Because
there is overlap of sensors a small target materials piece may be
detected by multiple sensors in different rows of the sensor array.
The overlap can improve the performance of the system by adding
some redundancy to the target material detection. The overlap may
be quantified by a percentage. For example, a sensor array may have
a 33% overlap if one third of each sensor is overlapped with
another sensor. For a high level of redundancy, the overlap
percentage can be 50% or higher, Adding more rows to the array,
using larger diameter holes or placing the sensors closer together
can increase the overlap.
[0057] After the fine stainless steel, aluminum/copper radiators,
circuit boards, low conductive precious and semi-precious metals,
lead, insulated wire and other nonconductive scrap pieces are
sorted, they can be recycled. Although it is desirable to perfectly
sort the mixed materials, there will always be some errors in the
sorting process. The fine stainless steel, aluminum/copper
radiators, circuit boards, low conductive precious and
semi-precious metals, lead, insulated wire and other nonconductive
scrap sorting algorithm may be adjusted based upon the detector
signal strength. With analog sensors, a strong signal is a strong
indication of metal while a weaker signal is less certain that the
detected piece is metal. An algorithm sets a division of metal and
non-metal pieces based upon signal strength and can be adjusted,
resulting in varying the sorting errors. For example, by setting
the metal signal detection level low, more non-metallic pieces will
be sorted as metal. Conversely, if the metal signal detection level
is high, more metallic pieces will not be separated from the
non-metallic pieces. The metal recycling process can tolerate some
non-metallic pieces, however this sorting error should be
minimized. The end user will be able to control the sorting point
and may even use trial and error or empirical result data to
optimize the sorting of the mixed materials.
[0058] Although the described metal sorting system can have a very
high accuracy resulting in metal sorting that is well over 90% pure
metal, it is possible to improve upon this performance. There are
various methods for improving the metal purity and accurately
separating the fine nonferrous metals and insulated wire from mixed
non-metallic materials at an accuracy rate close to 100%. The metal
sorted as described above can be further purified by further
sorting with an additional recovery unit. The recovery unit is
similar to the primary metal sorting processing unit described
above. The fine stainless steel, aluminum/copper radiators, circuit
boards, low conductive precious and semi-precious metals, lead,
insulated wire and other nonconductive scrap pieces sorted by the
primary metal sorting unit are placed onto a second conveyor belt
and scanned by additional arrays of inductive proximity detectors
in the recovery unit. These recovery unit detector arrays can be
configured as described above.
[0059] Like the primary sorting unit, the outputs of the inductive
proximity detectors are fed to a computer which tracks the fine
stainless steel, aluminum/copper radiators, circuit boards, low
conductive precious and semi-precious metals, lead, insulated wire
and other nonconductive scrap pieces. The computer transmits
signals to the sorting mechanism to again separate the metal and
nonmetal pieces into different bins at the end of the conveyor
belt. In the preferred embodiment, the sorting system used with the
recovery unit has air jets mounted under the plane defined by the
upper surface of the conveyor belt. The air jets are not actuated
when the non-metal pieces arrive at the end of the conveyor belt
and they fall into the non-metal bin adjacent to the end of the
conveyor. The recovery computer sends signals actuating the air
jets when metal pieces arrive at the end of the conveyor belt
deflecting them over a barrier into a metal bin. These under
mounted air jets are preferred because the metal tends to be
heavier and thus has more momentum to travel further to the metal
bin than the lighter non-metal pieces. The resulting fine
non-ferrous and insulated wire pieces that are separated by the
recovery unit are at a very high metal purity of up to 99% and can
be recycled without any possible rejection due to low purity.
[0060] Because the majority of the parts being sorted by the
recovery unit are metal, there will be much fewer pieces sorted
into the non-metal bin than the metal bin. Because there will be
some metal pieces in the non-metal bin and the total volume will be
substantially smaller than that in the metal bin, the pieces in the
non-metal bin may be placed back onto the recovery unit conveyor
belt and resorted. By passing the non-metals through the recovery
unit multiple times, any metal pieces in this material will
eventually be detected and placed in the metal bin. This processing
insures the accuracy of the metal and non-metal sorting.
[0061] It will be understood that although the present invention
has been described with reference to particular embodiments,
additions, deletions and changes could be made to these
embodiments, without departing from the scope of the present
invention.
* * * * *